Proximal Convoluted Tubule (PCT)

This is the first part of the renal tubule and it lies in the cortex of the kidney, close to the renal corpusle. Fluid that is filtered from the Bowman’s Capsule enters into the proximal tubule. It contains brush border, and is made up of cubiodal epithelium. It has an acidophilic cytoplasm due to the number of mitochondria.

Collecting Ducts

The CD runs through the cortex into the medulla and opens into the renal papilla. Its epithelium varies from cuboidal to columnarepithelium(near the papilla). It is the final segment of the renal tubule. It has two types of cells:

These functions are regulated by ADH and aldosterone. Aldosterone increases sodium reabsorption and increases potassium secretion. ADH on the other hand enhances water reabsorption. Therefore one can say that when ADH is increase water in the tubule is reabsorbed casuing a low volume concentrated unrine. Decrease ADH will result in a diluted high volume urnine.